“Buy the nicest, most supple tires you can afford; and buy them in the widest width that you can fit in your frame.”

That is Joshua Poertner’s summary of a panel discussion on Cyclingtips.com. Joshua used to be the president of Zipp, the makers of super-fast aero wheels, and he did a lot of research on how to make your bike faster.

The panel included Joshua, cycling journalist James Huang, and me, with Elden Nelson (who runs the blog “The Fat Cyclist”) moderating. The goal was to explain the science behind the current trend toward wider tires to an audience of racers and performance riders, who want to understand how to make their bikes faster.

In the podcast, we talk about why narrow tires feel faster, but aren’t. We discuss how lower pressures increase the internal resistance as the tire flexes, but decrease the suspension losses from the vibrations of the bike – the two effects cancel each other, hence your speed doesn’t change.

We also talk about the history of this research. I was amazed to find out that Zipp had been doing similar research to our own. They were trying to optimize tire pressures for the professional racers they sponsored. During their testing on rough surfaces like the cobbles of Paris-Roubaix, lowering tire pressure made their racers faster – until their wheels broke. The next step was to go to wider tires, so the wheels could survive… And then they found that even on smooth roads, lower pressures and wider tires were faster. They considered these findings “trade secrets”, and yet the other teams just had to read Bicycle Quarterly to get the same information. And eventually they did…

To me, Joshua’s conclusion really is remarkable: “Buy the most supple and widest tire you can fit in your frame.” His words could just as well have been mine. To have the guy who designed wheels for Zipp say this… It shows that the wide tire revolution has reached cycling’s mainstream.

29 Responses to Panel Discussion: The Wide Tire Revolution

How can a regular person determine what is functionally a supple tire? The data that Bicycle Quarterly and this blog provided with the soap box derby hill is very difficult to duplicate without buying samples of every tire…

Like any in-depth research, it’s not something you can do in an afternoon with limited means. We’ve done some of it for you, testing a large number of tires. Generally speaking, the high-end racing models are supple: Vittoria Open CX Corsa and similar types, but most of them don’t come wider than 25 or 28 mm. That is why we developed our Compass tires – we couldn’t find the tires we wanted to ride.

I have purchased 4 sets of Compass tires for the bicycles that fit them. Chinook Pass on my road bike, Barlow Pass on my touring bike, and Slumgullion Pass on my oldest son’s bicycle. I have recently been enjoying the Rat Trap Pass tires on some fast gravel grinders – much better than the WTB Nano tires I had been using. The problem is finding equally supple tires for muddy and wet mountain biking, a front studded snow tire for very slick icy dirt roads in Michigan wintertime, and 20″ and 24″ tires for my younger kid’s bicycles. Have you considered making the unshaved prototype version of the Rat Trap Pass and other tire sizes available? It appears to be a market that other tire manufacturers aren’t pursuing.

We are thinking about tires with tread that works better in mud and snow. As you say, that is the one place where a “road” tire with minimal tread doesn’t perform well. The minimum quantities of tire manufacture make this a big decision – is there a significant market? – but we are thinking about it.

I wonder if we can go further into the research of optimum tyre deflection. Aircraft tyres are designed to operate at an optimum tyre deflection, and pressure ranges are given to ensure charted tyre deflection is maintained when aircraft weight and runway surface is changed. I think this applies to bikes as well. Cheaper bike tyres do not have very good sidewall flexibility, and consequently have quite a narrow operating range when it comes to tyre deflection. Wouldn’t it be wonderful if bike tyre manufacturers provided this type of data? You could identify tyre quality just by looking at the deflection range on the sidewall.

Great conversation on the podcast, Jan. So much to discuss, and grip was barely addressed, let alone tread and aerodynamics. Since riding the extralight 32mm Stampede Pass tires from Compass for the first time a couple years ago, I’ve been thinking they would be the ideal tire for the typical road cyclist. Cool to see now that Poertner, Huang, and Heine are thinking the same. We just need more bikes, and affordable ones, that can fit nice, supple tires like them, and disc brakes is making that easier. On the aero side, I am eager to see data on tires up to and around 50mm wide!

The relationship between width, rolling resistance & aerodynamics is a question for me too. My experience is that there was no discernible difference in my average speeds when running 28 mm Continental 4xSeasons and 35 mm Bon Jon Pass, but a whole lot of difference in comfort, grip, and ability to ride on rougher roads. But one of your posts was from someone in the gravel racing world who claimed he could feel the aero difference between running 32 mm and 35 mm. I’m certainly no racer but I’m interested to know what sort of differences aero rims appropriate to 35 mm tyres (or 42 or 54 mm, for that matter) might make. I’ve been trying to reduce wind resistance as much as possible: I might ride at low speeds, but I’m sure the wind is a bigger factor than weight (I feel I should admit to doing 200 km audaxes in moving times of c.8 to 8.5 hrs—the elapsed times might be anything from 9 to 11 hours depending on mood, sleep, and Devonshire tea opportunities: I think that makes me about average for a 60 year old with some injuries but I’ll accept any improvements I can make.)

And on a related issue, in the podcast you alluded to the wind tunnel tests you’ve done and I seem to remember you wrote that mudguards made no difference to aerodynamics. Again, my experience is I’m no slower when I ride with mudguards than without, but I don’t know why that should be so. Surely a wide mud flap catches the wind? And are aero rims any help when you use mudguards? (In Australia most audax riders use low section aero rims and 25 mm tyres and only minimal mudguards if at all: myself, I like to be dry.)

We tested a lot of those things in the wind tunnel – see Bicycle Quarterly 21. Wider tires make little difference – both with an without fenders, the difference between 25 and 31 mm tires was too small to be statistically significant. Good fenders are neutral, too – no increase in drag. The front part (in front of the fork crown) decreases drag, the rear increases drag, so if you want to go faster, install fenders that only extend forward of the fork crown.

Generally, a cyclist is not a very aerodynamic shape, so it’s the frontal area more than anything that determines wind resistance. When you at a bike that way, 20 mm extra tire width makes little difference. Probably less than 20 mm wider handlebars…

On my old steel tourer big, fat Michelin World Tour tyres were faster than 1 1/8″ or 1 1/4″ tyres. The extra air smoothed out the stiff ride more than lighter, thinner and slicker tyres could.
I now ride a Trek Domane. I pump my 25C to 95-100psi; a little bit higher because I weigh 110kg.
I wonder what the optimal tyre pressure and width would be on an endurance bike with a bit of give like the Domane, Roubiax or Synapse?

That was a great listen. I’m so happy “gravel/adventure bikes” have gone mainstream as wheel clearance has thankfully increased on many affordable production bikes. The wide tire evolution is great for everyday cyclists. The podcast mostly concentrated on speed and comfort and performance benefits of supple wide tired & how suspension losses work into the equation – all great talking points, but just wanted to add: I work at a bike shop and always talk to my bigger customers (200++ pounds) about the comfort benefits of wide tires, and how it’s easier on your body (and wheels) not to be 280 pounds rolling on 700×25 tires inflated to 120 psi. Crazy how some shops sell bikes with tiny spoke counts to the bigger folks out there.

Hi Jan, I have been fascinated with your research and listened to the podcast yesterday. I then went out and lowered my tire pressure to 75F/85R on the 25mm tires. I am 160 lbs, 70 years old and riding a Domane 6.5 Di2 withDura-ace AC35 wheels. I was amazed; used 1 less gear on the climbs (tops at 9.5% grade) and was faster and more comfortable on the rough pavement and train trail.
Thank you; simply amazing. I am going to build a gravel bike and will use a minimum of 42mm tires on wide rims.

Great podcast. You made a few points in ways that never made it in print, but make the verbal conversation very visceral. This must be my first time hearing you speak, so there was that moment of surprise, like when you read a book, then see the movie, and the voices don’t match the ones in your head.

I too wonder if there is a point where aerodynamics start to kick in. “As big as you can fit” is rarely even 28mm on the newest “road” bikes. But since all my bikes, for many years, have been custom built for 38mm or larger tires, it is tempting to try a production bike designed for aerodynamics with skinny 32 or 35mm tires. Smaller than that I refuse to go.

Good question, and it really depends on the use. For mostly paved use, I’d run 42s. They are less sensitive to tire pressure and give you more freedom in designing the bike. If the bike was used mostly on gravel, I’d go with wider tires, though.

A third explanatory factor that I think will re-enter the discussion at some point is tire compounds. Essentially how the rubber interacts with road imperfections and the force required to be released from the imperfections. This is separate from hysteresis and suspension losses and for a while was the thought to be the “only” factor of interest.

I suspect this is one of the reasons Continental tires roll as well as they do, because it sure isn’t the result of supple casings!

That is an interesting subject. Of course, our tire testing (real roads, real rider) takes all those factors into account, but we aren’t able to separate them. For that, testing with a weighted wheel alone on a very smooth asphalt surface might be best… I doubt it’s a huge factor – no tread rubber is so sticky that it really sticks to the asphalt. Except perhaps the 650B tires from a few years back that had something like suction cups in their tread pattern.

We are talking about micro-second interactions and tire squirm, so I am not sure perceived tackiness is a fair comparisons. Anyway, in light of all the solid discussion of suspension losses, I struggle to understand why continental Gatorskins rated well as they did in your original test; the casings are like riding bricks.

I also noticed compound was the only place I thought compass tires could improve, mainly wet condition traction. I did some personal slide tests with Specialized, Continentals and Compass tires and found the compass were easiest to get to break free in the rain. (Not the kind of test for the faint of heart, let me tell you).

I begrudgingly hang up my compass tires once the rain starts coming out in force.

I am surprised by your impressions, since we’ve found the Compass tires to offer excellent grip in the wet. Here is a photo of the “BQ Team” during a wet and cold mid-winter descent… The second rider, Hahn, was on Conti tires. He lost grip in the next corner and went off the road as he opened the radius to prevent wiping out. Fortunately, no harm was done except a taco’ed front wheel, but it didn’t give us the impression that the Contis offered better grip than our tires. Hahn’s skills are as good as anybody’s, so it’s hard to fault the rider.

Tire compound makes a huge difference in the speed of the tire. It is the #1 factor over casing pressure or size. I have tested so many tires and I can tell you what brands/compounds are super fast and which ones can barely roll down the road. There are also a few websites that list watts lost @ at whatever speed from tested tires, from what i’ve seen most of them are relatively accurate.

If you test tires on a steel drum, then tire compound is very important, and a harder compound rolls faster. On real roads, softer compounds roll faster, as they don’t vibrate as much. So unless the tests are done on real roads, with a rider on board, the results are misleading.

For example, in our initial tires tests, we tested both the Michelin Pro2 Race and the Continental Ultra Gator Skins. When TOUR tested these tires on a steel drum, the harder Michelins rolled much faster. In our real-road testing, both tires rolled at the same speed – the more supple casing of the Michelins was negated by the harder tread rubber. (To say nothing of the poor grip of the harder rubber.)

Loved the podcast. Like many here, I’ve read all your great work on the subject and yet still gleaned plenty of new insights.

Your comment towards the end about pro racers suspending themselves beautifully, over road bumps….cannot be overstated.

Its something you barely hear discussed, but its a very significant variable in the difference between dangerous and highly skilled bike riding.

And as important as that is one road, as someone who rides 90%+ dirt, I’d say one’s ability to suspend the body in an ideal fashion is significantly more important on rough singletrack as compared to road.

If you look at BMX or Motocross, those guys are really throwing their bodies and bikes around to ideally manipulate their particular contact with the ground.

I have been a convert for years to the widest tire on wide rim / lowest pressure for years now… and I’m all about Compass Extralight for road/gravel….

My one remaining question: Without having done the research… what is your guess when it comes to nasty, tire chewing MTB trails, is zero sidewall protection, “as supple as you can get,” still the way to go?

I really don’t have much experience riding gnarly singletrack. It seems that pro mountain bike racers are split, some buying hand-made FMB tubulars, others racing slightly stiffer tires. Another factor is the ability to climb out of ruts. A supple sidewall at low pressures will deflect a lot in that situation, affecting your steering. Obviously, some racers decide it’s not a big deal or worth the trade-off against the superior speed of the supple tires, others do not.

If I am not mistaken Mike Hall served along side of you as a judge in the recent technical trials in Paris. Needless to say Mike has a very impressive track record for success in self supported ultra endurance events (record holder for Tour Divide and Trans-Am). Mike’s tire choices seem to contradict your approach to an extent (higher pressures, smaller widths). Of course Mike could be succeeding in spite of his choices rather than because of them – he is obviously a very talented rider physically and mentally. Did you have an opportunity to talk to him and get his take on these matters? I think a lot of of readers like me who respect you a great deal still are trying to figure out what the best dirt/gravel tire setup would be for an extended tour with varied conditions and weather (ex: Tour Divide).

I was looking forward to talking to Mike Hall, but the opportunity did not arise. Unfortunately, he was a no-show at the French Technical Trials, and had to be replaced with a last-minute addition to the jury.

In Europe, the new science about tires has not yet pervaded the mainstream. Riders there still are arguing that 20 mm tires are faster than 23s. However, since the Tour de France pros all are on 25s now, it’s only a matter of time until the rest emulate that practice.

When you see the number of riders with backpacks at the start of PBP, you might think that a backpack is a viable option for carrying your supplies on a 1200 km ride. When you talk to these riders late in the ride, they all complain about back problems. I am sure that their equipment seemed like a rational decision before the start, but it turned out to be faulty.

Our job is provide science based on rigorous testing that enables people to make more rational decisions. I was encouraged during the recent panel discussion with Josh Poertner when I learned that Zipp, the maker of high-end wheels, had done similar research to ours and come up with the same results.

We can only figure out what is faster, what absorbs shocks better, etc. We provide the knowledge, but riders have to make their own decisions that take many factors into account, including personal preference and aesthetics. That is how it should be.

The lean bike is to safely teach how far one can actually lean the motorbike, without the expensive scraping on the ground when one pushes it too far. A similarly modified bicycle would allow measuring lean angles and G forces, again without much risk to rider or equipment.

Wow, that slide bike looks really neat! They use it to teach you how to drift the bike, not how to catch it after you lose traction accidentally. Catching a bike that lost traction almost always leads to high-siding, which is far worse than just sliding out.

TOUR magazine in Germany tried to quantify cornering grip – first with a wheel that they dragged behind a car, measuring the forces it generated as it slid. Then they built a scooter and had a stuntman ride it in tighter and tighter radii, until he crashed. Unfortunately, there were too many variables to obtain repeatable results.

The best product development often is based on experienced riders feedback. That is our excuse why we ride our bikes so much!

As to learning to feel the limits of traction, snow and mud are great for that. On slippery surfaces, you can actually recover from a front-end slide. This allows you to get a feel for when the bike is about to lose traction, which is extremely useful on the road. Good tires actually send you feedback on how much grip you have left, so you can approach the limit without overstepping it.

Jan, the podcast discussion between you and Josh was a joy to hear. Now us old guys (most of the guys I ride with) can get the young riders to understand why us old guys love wide tires as they will listen to a podcast cast but won’t take the time to read about it.

These days, when I ask a riding buddy “What pressure are you running on your [road] bike today?” – we all just understand “How low can you go and live with it?”. You’d think we were racing CX again!